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Drilling holes in plastic

Centering holes drilled in distributors, heads, or exhaust pipes is important, but I have found that when I drill small holes in plastic, I can’t see the hole! To solve this problem, I color the area to be drilled with a black Sharpie marker. Now, when I start a pilot hole, it really stands out against the color of the marker.

Another trick is to start the pilot hole with a smaller bit than you need for the hole being drilled. That way, if this “starter hole” is off-center, any adjustment can be made before you get very far under the surface. Small adjustments can be made by angling the bit toward the center of the piece and slowly drilling until the bit is centered. Stand the bit up to a vertical position, and you’re set to go.

After the starter hole is centered, change to the desired larger-sized bit to create a centered hole every time. The Sharpie ink doesn’t penetrate the plastic, and can be easily sanded off after the hole is drilled. Be sure to sand off the ink, though, because it might bleed through the primer.Centering holes drilled in distributors, heads, or exhaust pipes is important, but I have found that when I drill small holes in plastic, I can’t see the hole! To solve this problem, I color the area to be drilled with a black Sharpie marker. Now, when I start a pilot hole, it really stands out against the color of the marker.